1. Field of the Invention
This invention relates to volume circuits that use resistive ladder circuits for adjustments of audio signals in volume levels.
2. Description of the Related Art
In the fields of audio devices and technologies, electronic volume circuits for fabricating electronic circuits are conventionally used for adjustments of volumes in audio signals. Japanese patent application No. 2000-28152 (i.e., Japanese Unexamined Patent Publication No. 2001-217660; and U.S. patent application Ser. No. 09/773,646) disclosed an example of an electronic volume circuit that is driven by a single power source and whose components are fabricated together as LSI circuitry.
In the aforementioned electronic volume circuit, the gain (or attenuation) of an input signal is controlled by selecting a tap (or a voltage division point) from series resistance. In particular, when the gain is greatly narrowed down, resistance division points should be extremely reduced in resolutions when selected. Therefore, it is difficult to accurately and sufficiently narrow down the gain of an input signal in a conventional electronic volume circuit.